US ZIP Code Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching us zip code, ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// US ZIP Code
// ReDoS-safe | RegexVault — Localization > Postal Codes

const usZipCodeRegex = /^([0-9]{5})(?:-([0-9]{4}))?$/;

function validateUsZipCode(input: string): boolean {
  return usZipCodeRegex.test(input);
}

// Example
console.log(validateUsZipCode("10001")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Postal Codes category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Capture group 1: 5-digit ZIP, group 2: ZIP+4 extension. ZIP codes start from 00001 (Adjuntas, Puerto Rico) to 99950 (Ketchikan, Alaska). Ranges are not evenly distributed — 00001-00999 is Puerto Rico territory.